Hybrid electro-mechanical transmissions are known to improve the exhaust emissions of a vehicle in that the electrical power reduces the fossil fuel used in the prime mover. Also, present in the prior art are input split, parallel hybrid type transmissions, one of which is disclosed in U.S. Pat. No. 5,558,588, assigned to the assignee of the present invention.
The hybrid electro-mechanical transmissions are constructed such that the engine and electric motor drives or generators are combined at the input to provide an input split between the utilization of the power sources. The power from the prime mover and the motor/generator sets is combined in one or more planetary gearsets to provide an output power which is then utilized to drive a vehicle. The vehicle can be as large as an earthmover or tank, and as small as a passenger car.